1. Field of the Invention
The present invention generally relates to a capacitor, and more particularly, to a capacitor having a substantially flat, planar geometry. Still more particularly, the present invention relates to a metallic substrate provided with capacitive material contacted thereto and incorporated into a hermetically sealed casing to provide at least one of the electrodes for the capacitor. The metallic substrate can provide at least one of the casing side walls itself or be connected to the side wall. A most preferred form of the capacitor has the conductive substrate provided with pseudocapacitive material formed from an ultrasonically generated aerosol.
2. Prior Art
Standard capacitor construction consists of a cylindrically shaped case housing an anode electrode and a cathode electrode. For example, standard wet slug tantalum capacitors generally have a cylindrically shaped conductive casing serving as the terminal for the cathode electrode with the tantalum anode connected to a terminal lead electrically insulated from the casing by a glass-to-metal insulator and seal structure. The anode insulator and seal structure is disposed either internally or externally of the casing. The opposite end of the casing is also typically provided with an insulator structure. The cylindrical shape limits the internal volume inside the capacitor and the closing seal structures occupy volume that detracts from the capacitor's volumetric efficiency.
Furthermore, the capacitor of the present invention having a flat, planar shape can comprise either an electrochemical type capacitor or an electrolytic type capacitor. The anode and/or the cathode in an electrochemical capacitor or the cathode in an electrolytic capacitor generally include a substrate of a conductive metal such as titanium or tantalum having a capacitive material provided thereon. In that respect, the capacitive material may be in the form of an anodized-etched foil, a sintered active material with or without oxide, a double layer capacitive material such as a carbonaceous capacitive material or platinum black, a pseudocapacitive material such as a redox or under potential material, and conducting polymers. Commonly used coating techniques include dipping, sputtering and pressurized air atomization spraying of a solution of the capacitive material onto the substrate. Capacitance values for electrodes made by these prior art techniques are lower in specific capacitance than an electrode coated with an ultrasonically generated aerosol of active material according to the present invention. Sol-gel deposition is another prior art method of coating a substrate, and this method also provides capacitor electrodes lower in specific capacitance than ultrasonically generated aerosol coatings.